1. Field of the Invention
The present invention generally relates to a communication network, and more particularly to a communication receiver and a communication receiving method.
2. Description of Related Art
Ethernet is a computer networking technique that is widely used in constructing a local area network. 10BASE-TX, for example, is specified in IEEE 802.3 and can transfer data at a nominal rate of 10 Mbit/sec. Data is transferred over an unshielded twisted-pair (UPT) cable with a specified length.
FIG. 1 shows a representative waveform of a frame structure of Ethernet over twisted pair running at 10 Mbit/sec (or 10BASE-T). A frame is separated from other packets by silence signal, during which no transactions occur. Each frame includes four parts: a preamble, a start of frame delimiter (SFD), data and an end of transmission delimiter (ETD). The preamble commonly includes a pattern alternated with “0” and “1,” which are used for the purpose of synchronizing a receiver. At the end of the preamble is the SFD, which includes a specific pattern (e.g., 10101101 as shown in FIG. 1) that is used to determine the beginning of the data. Following the data is the ETD (e.g., a predetermined period of high level before returning back to zero level) that is used to indicate the ending of the frame.
However, the frequency and phase of a received signal's carrier are commonly deviated from those of local oscillator. Moreover, as the UPT cable length is expanded, aged or disposed in a noisy environment, the received signal at the receiver side may probably be decayed or have lower signal-to-noise ratio (SNR). As a result, the received signal at the receiver side may probably be decayed or have lower signal-to-noise ratio (SNR), therefore increasing data error or reducing detection ratio.
For the reason that the conventional Ethernet receiver could not effectively receive data in a noisy environment, a need has arisen to propose a novel scheme for recovering a symbol from the received signal.